The invention relates to a filing device for layers of sheets provided with holes. A one-part folded body is separated from a flat, flexible blank having a substantially constant thickness, such as a plastic film, sheet or the like and forms two fastening sides movable through a folding joint zone between an opened out and accessible position and a folded, closed position with the insides thereof against one another. One of said sides as a threading or sequencing side has at least two threading or sequencing tongues for receiving layers of sheets via holes and whereof the other as a counter-side for each sequencing or threading tongue is provided with an insert opening for each tongue in a raisable insert strip and into which the associated sequencing tongue can be inserted from its sequencing position into its filed position.
A filing device of this type is known (Offenlegungsschrift 26 12 625, dated Sept. 29, 1987), which is formed by a one-part punched piece in such a way that the fastening sides, sequencing tongues and insert strips are made from one piece. In this filing device, as is generally the case with such devices, it has not proved possible to achieve such a good function as in the case of multipart filing devices, particularly those in which the sequencing tongues are formed by separate, subsequently fixed components. The behaviour of the sequencing tongues during the opening and closing of the filing device could hitherto only be influenced by the choice of material and the cross-sections of the tongues, namely in that the tongues are made in a relatively hard resilient manner from a different material than the fastening sides. In the case of the known one-part device, the sequencing tongues are made from the same flexible material, i.e. less bending-elastic than bending-soft or slack material, so that there is a risk in the case of said tongues that they will become folded over themselves in the fastening position during the closing of the filing device and can consequently become permanetly bent. This can also not be prevented in that the sequencing tongues in conjunction with the insert strips are constructed in such a way that the tongues are pulled instead of pushed through the insert openings of the insert strips, i.e. engaged in the openings in the strips with a much higher frictional resistance than their bending strength although said frictional resistance is smaller than their tensile strength. If bending of the sequencing tongues is to be avoided on closing the filing device, it is necessary to pull manually inside of the counter-side, on the ends of the sequencing tongues projecting through the insert strips until the filing device is folded shut, so that the strips are displaced in accordance with the shortening of the distance between said strips and the tongue heels. However, as this is very cumbersome and as even a single handling error can lead to permanent deformation of at least one sequencing tongue, said filing device has not been adopted, although there is a very pronounced need for a one-part, but correctly functioning filing device due to the particular advantages resulting from the fact it cannot be destroyed, has a low weight, a limited spatial extension and is esthetically pleasing.
These advantages also fail to appear in known multipart filing devices (U.S. Pat. No. 2,773,504). They are also much more complicated to manufacture, rivets or clips being required for fixing individual folding layers to one another. In particular separate sequencing tongues are required whose material characteristics are adapted to requirements. Although these sequencing tongues will bend, they are resistant to bending, i.e., they have a certain stability with respect to their bending resistance in the particular bending state. This is intended to achieve that on folding together or closing the fastening sides, the sequencing tongues automatically slide into the insert openings under the stresses which occur and consequently adapt their position to the position of the insert strip. However, it has been found that the use of a flexible sequencing tongue with a certain stability in the bent shape still cannot prevent there being such a large jamming force between between counter-side and sequencing tongue when closing the fastening sides that the sequencing tongue folds over on itself instead of sliding and therefore becomes unusable due to the formation of a bend point or kink.